This application claims the priority of Korean Patent Application No. 10-2004-0009841, filed on Feb. 14, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a method for real-time detection of polymerase chain reaction (PCR), and more particularly, to a method for detecting whether or not PCR is proceeding well by measuring in real-time the impedance change of PCR products as PCR is proceeding.
2. Description of the Related Art
Polymerase chain reaction (PCR) is method of amplifying DNA, for example it may include mixing DNA samples, polymerase and deoxyribose Nucleoside TriPhosphate (dNTP), adjusting the temperature of the mixture appropriately and amplifying the DNA.
The conventional PCR detection employs gel electrophoresis to show only the qualitative result of the amplified DNA after PCR is finished, and has many problems including an accuracy problem in quantitative detection of DNA. To solve this, real-time PCR devices have been developed, which enables the quantitative analysis of DNA by detecting the magnitude of fluorescence that is in proportion to concentration of amplified DNA, through an optical detection system.
So far, real-time PCR chips need a variety of optical apparatuses such as laser sources, micro mirrors, microscopes, and filters, and at the same, expensive fluorescent dye is used. In addition, for the purpose of using less samples and quickly performing analysis as well as decrease reduction in size of devices, PCR chips using a micro-electro-mechanical system (MEMS) have been developed. However, the real-time PCR chips have a problem in reducing the size in case of fluorescent detection, and an economic problem in case of using MEMS.
As another example of the conventional real-time PCR chip detection, there is a method for measuring impedance while PCR is proceeding in a solution. Theoretically, if PCR is performed in a solution, the impedance should show a sequential tendency as the PCR product increases. However, actually, a variety of materials are mixed such that it is difficult to find the tendency in relation to the PCR product. In addition, when the impedance is measured, as time passes by, the measured signal of the PCR product decreases due to non-singular adhesion of components of PCR samples other than DNA, for example, enzymes or PCR reaction buffers, in which the components are adhered to electrodes. Accordingly, the result according to the PCR cycle lacks repeatability. Also, due to the non-singular adhesion, change occurs on the surfaces of electrodes such that it is difficult to measure the PCR product itself generated in the solution.